Lipid requirements in growing japanese seabass (Lateolabrax japonicus) of two different sizes

Abstract

The optimal lipid requirements in Japanese seabass of two different sizes (initial body weight, 34.26±0.37 g, and 343.3±10.0 g) were tested using the same experimental diets in two feeding trials (trial I and trial II). Five experimental diets were formulated to obtain graded dietary lipid levels: 0.6%, 3.9%, 7.3%, 11.7%, and 15.8%. Each diet was randomly assigned to triplicate groups of fish. Both feed trials lasted 10 weeks. The results in both feeding trials showed that specific growth rate significantly increased by increasing dietary lipid levels from 0.6% to 7.3%, and declined thereafter. Based on the specific growth rate, the optimum dietary lipid requirement of the small and large Japanese seabass was 7.4% and 9.9% respectively. The increasing dietary lipid levels significantly increased the fish body protein concentration, but only in feeding trial II. In both feeding trials, the lipid contents in whole fish body and liver significantly increased with increasing dietary lipid levels, but the small fish showed much lower lipid content than the large fish. The serum triglyceride concentrations in the small fish were higher than those in the large fish. High levels of dietary lipid (3.9% and 7.3%) reduced the serum cholesterol concentrations in the small fish, which was much lower than those in the large fish. These results suggested that the lipid requirements, as well as the body composition and lipid deposition differed according to the size of growing Japanese seabass. The results are important for feed formulation for aquaculture of different sized Japanese seabass throughout their production cycle.